The invention disclosed herein relates generally to rotary shaft and lever actuators, and more specifically to a method and structure for reliably maintaining the radial position of a lever on a shaft while facilitating small angular adjustments in radial positioning. The invention has been found particularly useful in connection with rotary actuators for electrical limit switches.
Certain electrical limit switch designs, among a wide variety of other rotary shaft operated mechanisms, require a shaft having a radially extending lever attached thereto in a fixed radial position. A variety of methods and arrangements have been devised for accomplishing the desired attachment. One common arrangement is to grip or clamp the shaft in an aperture in a split end of the lever. Clamping may be accomplished by means of a bolt or screw extending at least partially through the split end.
It is known to further insure against slippage of the lever on the shaft by providing a knurled surface on the shaft in the form of a series of small ridges aligned with the shaft around the circumference of a segment thereof. As a lever is clamped onto the shaft, the ridges tend to bite into or deform the mating surface on the lever. This results in an attachment which is secure against circumferential slippage.
One disadvantage which has been experienced with the foregoing arrangement is that because the mating surface on the lever becomes deformed once the lever is attached, it is thereafter difficult to adjust the angle of the lever on the shaft between angular positions in which the ridges on the shaft coincide with indentations in the lever. This may be a significant problem where the actuator is part of a limit switch on a machine tool or other apparatus in which fine adjustment is important.
The applicant has discovered a method and structure which avoids this limitation on adjustability while maintaining the security against circumferental slippage afforded by a knurled surface on the shaft.